I think a lot of breakups are precipitated by people having or developing conflicting narratives in their heads about what relationships are, what makes them valuable, why people stay together, etc.

From my outside observations, I'd say that's very true. I think most people assume that everyone pretty much agrees what relationships are and what they're for, but I do not think that assumption is at all correct.

which can itself result in realizations like "this person fundamentally doesn't understand that relationship narratives can differ and is unwilling to discuss it" and that is also good information to have

That is good information to have!